August 02, 2014

'Fluffy And Feathery' Dinosaurs Were Widespread, Possibly Even Shrank To Become Small Birds

All dinosaurs were covered with feathers or had the potential to
grow feathers, a study suggests.

The discovery of
150-million-year-old fossils in Siberia indicates that feathers were much more
widespread among dinosaurs than previously thought.The find "has completely changed
our vision of dinosaurs", the lead researcher told BBC News.

The creature, called Kulindadromeus zabaikalicus, was
about 1m long, with a short snout, long hind legs, short arms, and five strong
fingers.

Its teeth show clear adaptations
for chewing plants.

Until now, fossilised evidence of
feathery dinosaurs has come from China and from a meat eating group called
theropods.

The latest discovery, in Russia,
is from a completely separate group of plant-eating dinosaurs called
ornithischians - which account for half of all dinosaurs.

Fluffy covering

The find takes the origin of
feathers millions of years further back in time than had previously been
thought, said Dr Pascal Godefroit of the Royal Belgian Institute of Natural
Sciences in Brussels, Belgium, who led the research."It was a big surprise," he
said.

"The fact that feathers have now been discovered in two distinct
groups, theropods in China and ornithischians in Russia means that the common
ancestor of these species which might have existed 220 million years ago also
probably had feathers."

The discovery has "completely
changed our vision of dinosaurs", he added."Instead of thinking of dinosaurs
as dry, scary scaly creatures a lot of them actually had a fluffy, downy
covering like feathers on a chick," said co-researcher Dr Maria McNamara of Cork
University in Ireland.

Alternative view

So do all the pictures of
dinosaurs in children's books need to be redrawn to make creatures like
Triceratops, Stegosaurus, Tyrannosaurus rex and the vicious
Velociraptor, fluffier and cuter?

Perhaps a little bit, according to Professor Mike Benton, of
Bristol University, who was also involved in the work.

"Our research doesn't mean that
all dinosaurs had feathers, especially as adults," he told BBC News.

"Some will have had feathers as
young animals and kept them throughout their lives. Others may have lost
feathers as they grew up, and became large enough not to need them, or replaced
feathers with scales or relied on bony plates in the skin for
protection."The key point is that dinosaurs
were all initially feathered and warm blooded, confirmation of an idea that has
prevailed for years, he said.

"Feathers were used first for
insulation and signalling; they only later became adapted for
flight."

But Dr Paul Barrett of the
Natural History Museum in London, has doubts.

"Most feathers have a branching
structure," he told BBC News.

"Instead these look like little
streamers coming from a central plate. No bird has that structure in any part of
its plumage and none of the developmental models that biologists use to
understand the evolution of feathers includes a stage that has anything like
that kind of anatomy."

Some 70 million years ago, three tyrannosaurs stalked together across a mud flat in Canada, possibly searching for prey.

The new insight comes from several parallel tyrannosaur tracks unearthed in Canada. The dinosaur tracks provide stronger evidence for a controversial theory: That the fearsome mega-predators hunted in packs.

The ferocious beasts may have "stuck together as a pack to increase their chances of bringing down prey and individually surviving," said study co-author Richard McCrea, a curator at the Peace Region Palaeontology Center in Canada. [See Images of the Giant Tyrannosaur Tracks]

Tyrannosaur huntingPaleontologists have long debated whether Tyrannosaurus rex and its cousins, such as Albertosaurus, hunted alone or in groups.

While most researchers believe the predators were lone wolves, so to speak, multiple Albertosaurus specimens found in a single bone bed in Canada's Dry Island Buffalo Jump Provincial Park have led some to propose that tyrannosaurs were pack animals.

But finding groups of bones together isn't definitive evidence for pack hunting, because bones can move after death. Other circumstances can cause fossil skeletons to accumulate in one location. For instance, many carnivores wandered individually into classic predator traps, such as the La Brea tar pits in Los Angeles, but probably didn't hunt together in life, McCrea said.

Track marks unearthedIn 2011, a local hunting outfitter and guide, Aaron Fredlund, unearthed two tyrannosaur track marks in the foothills of the Canadian Rockies in British Columbia and then told McCrea's team about the discovery.

The team eventually discovered a patch 197 feet (60 meters) long by 13 feet (4 m) wide filled with footprints from multiple dinosaurs, including tyrannosaurs, other small theropods, and duck-billed dinosaurs called hadrosaurs. These dinosaurs were apparently walking in the silty sediments from an overflowing river and formed the track marks about 70 million years ago. A thick layer of volcanic ash then preserved the marks, McCrea said.

In total, the team found seven tracks that were made by three tyrannosaurs. Though the researchers couldn't identify the specific species, it's likely given the period and location where they were found that Albertosaurus, Gorgosaurus or Daspletosaurus left the tracks, McCrea said.

Though the other dinosaur tracks there are all pointing in random directions, the tyrannosaur footprints are parallel with each other. The tyrannosaurs also left prints of about the same depth in the wet sediments, suggesting they crossed through the area at the same time. (As the mud dries, the depth of footprints becomes shallower.)

The new find may be one of the world's oldest examples of a missed connection. "The hadrosaur footprints are much more shallow, indicating that they came later," possibly just a few hours or days after the tyrannosaurs, McCrea told Live Science.

Pack animalsThe new tracks suggest that the tyrannosaurs may have hunted in packs to take down large prey, just as wolves do today.

"An individual wolf would not be able to take out a moose, but a pack of them would," McCrea said.

Similarly, pack hunting could explain how tyrannosaurs could kill hadrosaurs, which are almost as large as the predators, without sustaining horrific injuries, he said.

That doesn't mean tyrannosaurs would have been friendly to one another. In fact, other fossils reveal that the dinosaurs liked to head-bite each other. But the tyrannosaurs may have stuck together to hunt because it increased their odds of survival, McCrea said.

The new discovery also highlights the rough life of these hunters. One of the beasts was missing bones in its left foot, which is in keeping with many of the injuries found on other tyrannosaur specimens, McCrea said.

SCIENTISTS have mapped
how a group of huge, fearsome dinosaurs evolved and shrank to become small birds
such as hummingbirds and robins.

Comparing fossils of 120
different species and 1,500 skeletal features, especially thigh bones,
researchers constructed a detailed family tree for the class of two-legged
meat-eaters called theropods and found that they survive to this day as
birds.The steady downsizing and elegant
evolution of the theropods is detailed in the journal Science.

“They just kept on shrinking and
shrinking and shrinking for about 50 million years,” said study author Michael
S.Y. Lee of the University of Adelaide in Australia, who describes this suborder
of dinosaurs as “shape-shifters.”

Lee and colleagues created a
dinosaur version of the iconic ape-to-man drawing of human evolution. In this
version, the lumbering large dinos shrink, getting more feathery and
big-chested, until they are the earliest version of birds.

Scientists have previously linked
birds to this family of dinosaurs because they shared hollow bones, wishbones,
feathers and other characteristics. But the Lee study gives the best picture of
how steady and unusual theropod evolution was. The skeletons of theropods
changed four times faster than other types of dinosaurs, the study
said.

A few members of that dinosaur
family did not shrink, including T. Rex, which is more of a distant cousin to
birds than a direct ancestor, Lee said.

He said he and colleagues were
surprised by just how consistently the theropods shrank over evolutionary time,
while other types of dinosaurs showed ups and downs in body size.

The first theropods were large,
weighing around 270 kilograms, and roamed about 220 million to 230 million years
ago. Around 200 million years ago, when some of the creatures weighed about
165kg, the shrinking became faster and more prolonged, the study said. In just
25 million years, the beasts were slimmed down to barely 45kg. By 167 million
years ago, three kg paravians, more direct ancestor of birds, were
around.

And 163 million years ago the
first birds, weighing less than one kg, probably came on the scene, the study
said.

Paul Sereno, a dinosaur
researcher at the University of Chicago who wasn’t part of this study, praised
Lee’s work as innovative.The steady size reduction shows
“something very strange going on,” Sereno said. “This is key to what went on at
the origin of birds.”

People may think bigger is
better, but sometimes when it comes to evolution smaller can be better because
bigger creatures are more likely to go extinct, Sereno said.And when the theropods started
shrinking there weren’t many other small species that would compete with them,
Lee said.

“The dinosaur ancestors of birds
found a new niche and a new way of life,” Lee said.Sereno added, “When you are
small, it’s a totally different ball game. You can fly and glide and I think
that’s what drove it.”